HY USMLEQ#9  General Pathology Step 1

Level = Step 1 (inspired from Mehlman) 

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A 43-year-old man presents with night sweats, fever, and unintentional weight loss for the past 3 months. He works as an archaeologist. He recently returned from a hiking trip in Ohio River Valley. The physical examination reveals enlarged mediastinal lymph nodes. The lymph node biopsy reveals caseating granulomas with central necrosis.

Which of the following diseases is most likely associated with this histologic finding?

A. Crohn disease
B. Sarcoidosis
C. Histoplasmosis 
D. Foreign body reaction
E. Rheumatoid arthritis

 

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✅  Correct answer = Histoplasmosis

 

Education Objective:

Granulomas with central necrosis, classically seen in tuberculosis and fungal infections like histoplasmosis and cat-scratch disease ( Bartonella Henselae)

 

Caseating necrosis is seen in tuberculosis and some fungal infections due to a Th1-mediated immune response with high levels of IFN-Gamma and TNF-alpha, leading to macrophage activation and tissue destruction.

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❌ Choice A. Crohn Disease  and Choice B. Sarcoidosis= non-caseating granulomas

Crohn's disease and sarcoidosis have less aggressive immune responses than TB.
Granulomas in Crohn’s and sarcoidosis form to wall off antigens, but the inflammatory process does not cause the same level of tissue destruction.

Macrophages remain viable; there’s no extensive lipid release or protein breakdown that creates the “cheesy” necrotic center.

❌ Choice D. Foreign body reaction = non-caseating granulomas

❌ Choice E. Rheumatoid arthritis = non-caseating granulomas